/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.web.reactive.accept;

import org.springframework.http.MediaType;
import org.springframework.http.MediaTypeFactory;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.web.server.NotAcceptableStatusException;
import org.springframework.web.server.ServerWebExchange;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Resolver that checks a query parameter and uses it to lookup a matching
 * MediaType. Lookup keys can be registered or as a fallback
 * {@link MediaTypeFactory} can be used to perform a lookup.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class ParameterContentTypeResolver implements RequestedContentTypeResolver {

    /**
     * Primary lookup for media types by key (e.g. "json" -> "application/json")
     */
    private final Map<String, MediaType> mediaTypes = new ConcurrentHashMap<>(64);

    private String parameterName = "format";


    public ParameterContentTypeResolver(Map<String, MediaType> mediaTypes) {
        mediaTypes.forEach((key, value) -> this.mediaTypes.put(formatKey(key), value));
    }

    private static String formatKey(String key) {
        return key.toLowerCase(Locale.ENGLISH);
    }

    public String getParameterName() {
        return this.parameterName;
    }

    /**
     * Set the name of the parameter to use to determine requested media types.
     * <p>By default this is set to {@literal "format"}.
     */
    public void setParameterName(String parameterName) {
        Assert.notNull(parameterName, "'parameterName' is required");
        this.parameterName = parameterName;
    }

    @Override
    public List<MediaType> resolveMediaTypes(ServerWebExchange exchange) throws NotAcceptableStatusException {
        String key = exchange.getRequest().getQueryParams().getFirst(getParameterName());
        if (!StringUtils.hasText(key)) {
            return MEDIA_TYPE_ALL_LIST;
        }
        key = formatKey(key);
        MediaType match = this.mediaTypes.get(key);
        if (match == null) {
            match = MediaTypeFactory.getMediaType("filename." + key)
                    .orElseThrow(() -> {
                        List<MediaType> supported = new ArrayList<>(this.mediaTypes.values());
                        return new NotAcceptableStatusException(supported);
                    });
        }
        this.mediaTypes.putIfAbsent(key, match);
        return Collections.singletonList(match);
    }

}
